What is an ISR function?
An interrupt service routine (ISR) is a software routine that hardware invokes in response to an interrupt. ISR examines an interrupt and determines how to handle it executes the handling, and then returns a logical interrupt value.
What is the main difference between a function and an interrupt service routine?
3 Answers. The main difference between a function and a software interrupt is what is known as context. A function runs within the context of your main program. An interrupt runs within the context of the interrupt handler.
What is difference between ISR and subroutine?
Subroutine is a portion of code within a larger program, which performs a specific task and is relatively independent of the remaining code. Subroutine runs when you call it. ISR runs whenever a certain signal occurs. The big difference is that you know where the subroutine runs (because you call it).
Where is ISR stored?
Interrupt vectors are addresses which inform the interrupt handler as to where to find the ISR. All interrupts are assigned a number from 0 to 255. The interrupt vectors associated with each interrupt number are stored in the lower 1024 bytes of PC memory.
What is the difference between a function and a hardware ISR?
A function (or procedure or sub-routine more generally) must be explicitly called and is part of the same context and thread of execution as its caller. A hardware ISR is not explicitly called but rather invoked by some external event (external to the processor core that is – on-chip peripherals may generate interrupts).
What is the difference between ISR and function call ISR?
On ISR, the only register context stored is what is going to be used in the ISR. If one register is used, only that register is saved/restored. On most cpus, the register set stored/restored in a function call is much bigger than the ones stored/restored in an ISR due to the static nature of procedure calling conventions.
What is the difference between ISR and interrupt?
The interrupt is usually initiated by an internal (i.e. divided by zero, register overflow etc.) or a external signal (i.e. external pins of) microprocessor rather than the execution of instructions (i.e. software interrupt). After storing the current status of the program (i.e. value of PC ,PSW ) in the stack, the ISR is executed.
What is the difference between an ISR and a subroutine?
In the ISR of the keyboard, which is a part of the keyboard driver software, the processor will read the data from the keyboard. A subroutine (procedure/Subroutine) is a set of instructions needed repeatedly by the program. It is stored as a subroutine and called from several places by the main program.